DC UPS configured as intrinsic power transfer switch

ABSTRACT

A direct current (DC) uninterruptible power supply (UPS) configured as an intrinsic power transfer switch is provided. The DC UPS includes first and second inputs. First and second rectifiers are coupled to the first and second inputs. A common node is coupled to the first and second rectifiers. At least one DC output is coupled to the common node. The at least one DC output is adapted for connection to at least one electrical load. The first input is adapted for connection to a first electrical service, and the second input is adapted for connection to a second electrical service. The DC UPS continues to supply power to the at least one electrical load in the event of a loss of either the first or second electrical services.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to U.S. Non-Provisional application Ser.Nos. 12/174,381, 12/174,386, and 12/174,425 filed concurrently herewithand incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates in general to power supplies forelectronic devices, and more particularly, but not exclusively, todirect current (DC) uninterruptible power supplies (UPS) configured asintrinsic power transfer switches for use in computing environments.

2. Description of the Related Art

A controlled transfer switch is a common method to disconnect anelectrical service and connect an alternate service to a computersystem. Switching electrical services is often required when one serviceis lost and an alternate service is still functional.

FIG. 1 illustrates a conventional power transfer switch 11. Powerdistribution to electrical loads 13 and 15 from electrical services Aand B is managed by a variety of sensor and control equipment, includinga sensor 17 to monitor electrical service A, and a sensor 19 to monitorelectrical service B. Additional hardware 21 evaluates statuses of theelectrical services A and B, and provides the status information tocontrol transfer switch hardware 23, which provides the switchingfunctionality.

For the conventional switch as illustrated in FIG. 1, overt control isrequired to disconnect one electrical service and connection of another.The switching action can fail at the sensor, evaluation function, switchcontroller or at switch itself. This decreases availability andreliability of power to vital computer systems.

The sequence and timing of the transfer switch is important to theoverall functionality of the system. Two different electrical servicescannot be directly connected to the electrical load (computer system) atthe same time because of unmatched phase and frequency or greatlydiffering magnitudes. The switch must first disconnect a failed service,and then connect a functioning electrical service. This creates severalfailure modes. For example, the switch may fail to disconnect beforeconnecting, the switch may fail to connect after disconnection, or theswitch may connect before disconnecting.

In addition to the foregoing, in any conventional switching system thereis a delay or dead time associated with the transfer of power. This cancreate short gaps in power availability that the computer system's powersupplies must accommodate.

SUMMARY OF THE INVENTION

Multiple independent AC electrical power services are normally availablein information technology (IT) centers. The redundant feeds increaseavailability of power to computer systems. It is not possible todirectly combine AC sources of unmatched phase and frequency or greatlydiffering magnitudes.

A need exists for a mechanism to connect multiple redundant electricalservices that have unmatched phase and frequency or greatly differingmagnitudes without a transfer switch. Accordingly, in one embodiment, byway of example only, a direct current (DC) uninterruptible power supply(UPS) configured as an intrinsic power transfer switch is provided. TheDC UPS includes first and second inputs. First and second rectifiers arecoupled to the first and second inputs. A common node is coupled to thefirst and second rectifiers. At least one DC output is coupled to thecommon node. The at least one DC output is adapted for connection to atleast one electrical load. The first input is adapted for connection toa first electrical service, and the second input is adapted forconnection to a second electrical service. The DC UPS continues tosupply power to the at least one electrical load in the event of a lossof either the first or second electrical services.

In an additional embodiment, again by way of example only, an intrinsicpower transfer switch for a high-power electrical load requiring atleast two electrical service inputs is provided. A first direct current(DC) uninterruptible power supply (UPS) has a first output coupled tothe electrical load for driving the electrical load. A second DC UPShaving a second output is coupled to a first input of the first DC UPSfor driving the electrical load through the first DC UPS. The first andsecond DC UPS continue to supply power to the electrical load in theevent of a loss of either a first or second electrical service.

In still another embodiment, again by way of example only, a method ofmanufacturing a direct current (DC) uninterruptible power supply (UPS)configured as an intrinsic power transfer switch is provided. First andsecond inputs are provided. First and second rectifiers coupled to thefirst and second inputs are provided. A common node coupled to the firstand second rectifiers is provided. At least one DC output coupled to thecommon node is provided. The at least one DC output is adapted forconnection to at least one electrical load. The first input is adaptedfor connection to a first electrical service, and the second input isadapted for connection to a second electrical service. The DC UPScontinues to supply power to the at least one electrical load in theevent of a loss of either the first or second electrical services.

In still another embodiment, again by way of example only, a method ofmanufacturing an intrinsic power transfer switch for a high-powerelectrical load requiring at least two electrical service inputs isprovided. A first direct current (DC) uninterruptible power supply (UPS)having a first output coupled to the electrical load for driving theelectrical load is provided. A second DC UPS having a second outputcoupled to a first input of the first DC UPS for driving the electricalload through the first DC UPS is provided. The first and second DC UPScontinue to supply power to the electrical load in the event of a lossof either a first or second electrical service.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the advantages of the invention will be readilyunderstood, a more particular description of the invention brieflydescribed above will be rendered by reference to specific embodimentsthat are illustrated in the appended drawings. Understanding that thesedrawings depict only typical embodiments of the invention and are nottherefore to be considered to be limiting of its scope, the inventionwill be described and explained with additional specificity and detailthrough the use of the accompanying drawings, in which:

FIG. 1 is block/schematic diagram of a conventional power transferswitch;

FIG. 2 is a schematic diagram of an exemplary direct currentuninterruptible power supply (DC UPS) in which aspects of the presentinvention may be implemented;

FIG. 3 is a schematic diagram of the exemplary DC UPS depicted in FIG. 2configured as an intrinsic power transfer switch; and

FIG. 4 is a schematic diagram of a network of two exemplary DC UPSdevices collectively configured as an intrinsic power transfer switch.

DETAILED DESCRIPTION OF THE DRAWINGS

The illustrated embodiments below provide mechanisms for configuring oneor more uninterruptible power supplies (UPS) as an intrinsic powertransfer switch. In one embodiment, a single UPS device may be used. Inother embodiments, a series of interconnected UPS devices may be used.Where a series of interconnected UPS devices are implemented, suchconfigurations allow for automatic transfer of power between electricalservices even if the services are of unmatched phase and frequency, orof greatly differing magnitudes.

The illustrated embodiments require no overt action to route the powerfrom the functioning service to the electrical load(s). No overt actionis required to disconnect power from a lost or non-functioning service.No sensor, evaluation function, switch controller, hardware switch, oradditional hardware is required. In addition, no critical switchingsequence is needed. Finally, the illustrated embodiments allow for powertransfer switching functionality without transfer delays or powerdisruptions during transfer as described above.

A direct current (DC) uninterruptable power supply (UPS) device may beconfigured, either singly or in combination with additional devices, asan intrinsic power transfer switch. Turning to FIG. 2, an exemplary DCUPS 10 is illustrated for configuration as an intrinsic power transferswitch. It should be appreciated, however, that FIG. 2 is only exemplaryand is not intended to state or imply any limitation as to theparticular architectures in which the exemplary aspects of theillustrative embodiments may be implemented. Many modifications to thearchitecture depicted in FIG. 1 may be made without departing from thescope and spirit of the following description and claimed subjectmatter.

DC UPS 10 includes two or more inputs 12, and 14. In the depictedembodiment, two inputs 12 and 14 are coupled to an electrical service Aand B, respectively. In other embodiments, however, DC UPS 10 may beconfigured with three inputs corresponding to three electrical servicesA, B, and C, and so forth. Inputs 12 and 14 may accept alternatingcurrent (AC), direct current (DC), or partially or fully rectified ACpower.

Each of the inputs 12 and 14 are coupled to circuit protection devices18 and 20. Circuit protection devices 18 and 20 may, as one skilled inthe art will anticipate, vary for a particular implementation. Forexample, circuit protection devices 18 and 20 may include fuses, fuseelements, fusible links, circuit breakers, and the like as the skilledartisan will expect.

Circuit protection devices 18 and 20 are each coupled to a rectifier. Inthe depicted embodiment, full wave rectifiers 24 and 26 are showncoupled to circuit protection devices 18 and 20. Rectifiers 24 and 26may also include half wave rectifiers 24 and 26. The full waverectifiers 24 and 26 are coupled to a common node 30.

A battery 32 supplies backup current in the event of a power disruption.Battery 32 is coupled between ground 34 and a disconnect switch 36.Disconnect switch 36 is in turn coupled to a blocking diode 38.Disconnect switch 36 may be actuated by a controller 40. For example,disconnect switch 36 may be a relay or a similar device. Controller 40may provide a control signal to the disconnect switch 36 upon adetection of a power disruption from one or more of the inputs 12 and14. As one skilled in the art will expect, disconnect switch 36 mayinclude transistor devices, such as metal oxide semiconductor fieldeffect transistors (MOSFETs).

Circuit protection devices 42, 44, and 46 are shown coupled to thecommon node 30, and correspond to one of three DC outputs 54, 56 and 58.DC outputs 54, 56, and 58 are adapted for connection to at least oneelectrical load. The connected load(s) are shared between the outputs54, 56, and 58. Circuit protection devices 42, 44, and 46 may againinclude fuse and circuit breaker devices as previously described toisolate load faults. Disconnect switches 48, 50, and 52 may be coupledbetween the DC outputs 54, 56 and 58 and circuit protection devices 42,44, and 46. Here again, disconnect switches 48, 50, and 52 may include avariety of circuit elements and may optionally be controllable similarlyto disconnect switch 36.

DC UPS 10 rectifies input currents (e.g., input 12 and input 14). Theoutputs of each of the rectified currents are combined at common node30. Inputs 12 and 14 are rectified, then combined at common node 30.After the inputs 12 and 14 are rectified, they may be combinedindependently of phase, frequency or magnitude of the individual inputs.

An exemplary configuration 60 of a DC UPS 10 as an intrinsic powertransfer switch is shown in FIG. 3, following, with arrow 62 indicatingthe direction of current flow. Here, as in FIG. 1 previously, twoelectrical services (A and B) are provided. Input 12 of the DC UPS 10 iscoupled to the electrical service A. In the depicted embodiment, input14 is left unconnected. Input 16 is coupled to the electrical service B.

On the output side of DC UPS 10, output 54 is coupled through anelectrical load 64 to ground 66. Output 56 is left unconnected. In thedepicted embodiment, the sum of the input currents from electricalservice A and B is equal to the output current measured at output 54. Ifeither of the electrical services A and B is lost, electrical servicecontinuing to function will continue to supply power to the electricalload 64.

A second example of an intrinsic power switch uses a network 70 of twointerconnected DC UPS 10 devices as seen in FIG. 4, following, to supplya single high-power electrical load 72 that requires two electricalservice inputs. The output 56 of the first DC UPS 10 directly drives theload 72, and the second DC UPS 10 drives the load 72 through the firstDC UPS (output 56 of the second DC UPS is coupled to input 14 of thefirst DC UPS). Load 72 is coupled to ground 34. Each DC UPS 10 iscoupled to both electrical services, with an input 12 coupled toelectrical service A, and an input 16 coupled to electrical service B.

Here again, the sum of the input currents is equal to the output currentmeasured at output 56. To be able to operate from a single electricalservice in the event of a lost service, the sum of the currents to theload must be less than the sum of maximum available current from any twoinput power paths. If either of the electrical services A or B is lost,the other service will continue to supply power to the electrical load72. In addition, the depicted configuration may handle the loss of anyone input, coming from any input feed.

While one or more embodiments of the present invention have beenillustrated in detail, the skilled artisan will appreciate thatmodifications and adaptations to those embodiments may be made withoutdeparting from the scope of the present invention as set forth in thefollowing claims.

1. An intrinsic power transfer switch for a high-power electrical load,comprising: a first power supply; a second power supply independent ofthe first power supply; a first direct current (DC) uninterruptiblepower supply (UPS) including a first input coupled to the first powersupply, a second input coupled to the second power supply, a thirdinput, and a first output configured to be coupled to the electricalload and for driving the electrical load; and a second DC UPS includinga fourth input coupled to the first power supply, a fifth input coupledto the second power supply, and a second output coupled to the thirdinput of the first DC UPS, wherein the intrinsic power transfer switchcontinues to supply power to the electrical load in the event of a lossof either the first power supply or the second power supply.
 2. Thepower transfer switch of claim 1, wherein the first DC UPS includes: afirst rectifier coupled to the first input, a second rectifier coupledto the second input, and a first common node coupled to the firstrectifier and the second rectifier; and wherein the second DC UPSincludes: a third rectifier coupled to the fifth input, a fourthrectifier coupled to the fourth input, and a second common node coupledto the third rectifier and the fourth rectifier.
 3. The power transferswitch of claim 2, wherein the first, second, third, and fourthrectifiers are one of full wave rectifiers and half wave rectifiers. 4.The power transfer switch of claim 2, wherein the first DC UPS furtherincludes: a first battery coupled to the first common node, and a firstdisconnect switch coupled between the first battery and the first commonnode, and wherein the second DC UPS includes: a second battery coupledto the second common node, and a second disconnect switch coupledbetween the second battery and the second common node.
 5. The powertransfer switch of claim 4, wherein the first DC UPS further includes: afirst blocking diode coupled between the first battery and the firstcommon node, and wherein the second DC UPS includes: a second blockingdiode coupled between the second battery and the second common node. 6.The power transfer switch of claim 4, further including: a firstcontroller, wherein the first disconnect switch is adapted forconnection to the first controller for actuating the first disconnectswitch upon a first power loss; and a second controller, wherein thesecond disconnect switch is adapted for connection to the secondcontroller for actuating the second disconnect switch upon a secondpower loss.
 7. The power transfer switch of claim 2, further including afirst disconnect switch coupled between the first battery and the firstcommon node.
 8. The power transfer switch of claim 7, further includinga second disconnect switch coupled between the first common node and thefirst output.
 9. The power transfer switch of claim 2, further includinga disconnect switch coupled between the first common node and the firstoutput.
 10. The power transfer switch of claim 2, further including afirst disconnect switch coupled between the second battery and thesecond common node.
 11. The power transfer switch of claim 10, whereinthe second DC UPS further includes a third output configured to becoupled to the electrical load and for driving the electrical load. 12.The power transfer switch of claim 11, further including a seconddisconnect switch coupled between the second common node and the thirdoutput.
 13. The power transfer switch of claim 2, wherein the second DCUPS further includes a third output configured to be coupled to theelectrical load and for driving the electrical load, and furtherincluding a disconnect switch coupled between the second common node andthe third output.
 14. The power transfer switch of claim 2, wherein thesecond DC UPS further includes a third output configured to be coupledto the electrical load and for driving the electrical load, and furtherincluding: a first disconnect switch coupled between the first batteryand the first common node; a second disconnect switch coupled betweenthe first common node and the first output; a third disconnect switchcoupled between the second battery and the second common node; and afourth disconnect switch coupled between the second common node and thethird output.
 15. The power transfer switch of claim 1, wherein thefirst and second power supplies are direct current inputs.
 16. The powertransfer switch of claim 1, wherein the first and second power suppliesare alternating current inputs.
 17. The power transfer switch of claim1, wherein the first and second power supplies are partially rectifiedalternating current inputs.